The present invention pertains to a technical field of a buckle used in a safety belt device such as a seat belt device provided for a seat of a vehicle such as an automobile.
Nowadays, in various vehicles including automobiles, seat belt devices for protecting occupants in emergency such as collision are mounted for seats thereof. In order to facilitate the occupant to wear on and off such a seat belt, a buckle is normally provided. In general, the buckle comprises a latch member provided with a joggle portion which latches a tongue wherein the latch member is biased by a spring in such a direction as to latch the tongue.
In this case, when the spring force against the latch member is set to be weak in order to reduce the operating force for releasing the engagement between the tongue and the buckle, the force for latching the tongue to the latch member is weak. On the other hand, when the spring force against the latch member is set to be strong in order to increase the force for latching the tongue to the latch member, the operating force required for releasing the engagement is increased.
Therefore, the buckle is provided with a lock member which prevents the displacement of the latch member during the engagement with the tongue, thereby enabling the minimization of the spring force against the latch member and thus reducing the operating force for releasing the engagement. This technique has been used conventionally. As one of buckles of such seat belt devices, a buckle is disclosed in Japanese Utility Model Unexamined Publication No. 60-139560. The buckle is illustrated in FIG. 21 where a tongue is not engaged with the buckle and illustrated in FIG. 22 where the tongue is engaged with the buckle.
As shown in FIG. 21 and FIG. 22, the buckle 1' comprises a base 2', a latch member 3' pivotally supported by the base 2', a lock member 4' mounted on an upper surface of the latch member 3' to control the pivotal movement of the latch member 3' such that the lock member 4' can move relative to and pivot with the latch member 3', an operational button 5' for manipulating the lock member 4' which is slidably disposed to the base 2', an ejector 6' slidably disposed on a bottom 2c' of the base 2', a latch spring 7' always biasing the latch member 3', a lock spring 8' always biasing the lock member 4', a button spring 9' always biasing the operational button 5', and an ejector spring 10' always biasing the ejector 6', and a casing 11'.
As shown in FIG. 23, the base 2' comprises a U-like frame having side walls 2a', 2b' and the bottom 2c'. Both the side walls 2a', 2b' are provided with shaft holes 2d', 2e' and fan-shaped opening 2f', 2g' formed therein, respectively. The shaft hole 2d' and the fan-shaped opening 2f' formed in one side wall 2a', and, the shaft hole 2e' and the fan-shaped opening 2g' formed in the other side wall 2b' are positioned symmetrically about the longitudinal axis. The side walls 2a', 2b' are provided with restraint projections 2h', 2i' in positions around the fan-shaped openings 2f', 2g'. The bottom 2c' of the base 2 is provided with an opening 2j' formed in the center thereof.
As shown in FIG. 21 and FIG. 22, secured to an end portion of the base 2' opposite to the end through which the tongue 12' is inserted is a spring holder 13' supporting the respective one ends of the springs 7', 9', 10'.
As shown in FIG. 24, the latch member 3' is formed symmetrically about the longitudinal axis and comprises shafts 3a', 3b' which are inserted in and supported by the shaft holes 2d', 2e' of the side walls 2a', 2b', respectively, a joggle portion 3c' which can be latched to a latch hole 12a' of the tongue 12', shoulder portions 3d', 3e' which can pivot in the fan-shaped openings 2f', 2g', through holes 3f', 3g' formed in the shoulder portions 3d', 3e' to which the restraint projections 2h', 2i' can be inserted, respectively, a spring supporting and pressed portion 3h' which supports the other end of the latch spring 7' and is pressed by the operational button 5', and a spring supporting portion 3i' which supports one end of the lock spring 8'.
As shown in FIG. 25, the lock member 4' is formed symmetrically about the longitudinal axis and comprises control wings 4a', 4b' which controls the closing motion of the through holes 3f', 3g' of the latch member 3' in order to control the pivotal movement of the latch member 3', a spring supporting portion 4c' which supports the other end of the lock spring 8', and pressed portions 4d' which come in contact with the operational button 5' and are pressed by the operational button 5'.
As shown in FIG. 21, the operational button 5' comprises an operational portion 5a' which a seat belt user directly touches, a spring supporting and press portion 5b' which supports the other end of the button spring 9' and presses the spring supporting and pressed portion 3h' of the latch member 3', and a lock member press portion 5c' pressing the pressed portion 4d' of the lock member 4'.
The latch member 3' is always biased in the counter-clockwise direction .alpha.' about the shafts 3a', 3b' by the latch spring 7' and the lock member 4' is always biased against the latch member 3' by the lock spring 8' in the longitudinal direction .beta.' of the latch member 3'. Further, the ejector 6' is always biased by an ejector spring 10' in such a direction .gamma.' of ejecting the tongue 12'.
In the buckle 1' as structured above, when the buckle 1' is in non-engaged state (where the tongue 12' is not engaged and not connected) as shown in FIG. 21, the control wings 4a', 4b' of the lock member 4' are held in such positions that the wings 4a', 4b' are in contact with side edges of the restraint projections 2h', 2i' of the side walls 2a', 2b' and do not close the through holes 3f', 3g', i.e. such position that the wings 4a', 4b' are not in contact with the lower ends of the restraint projections 2h', 2i'. Therefore, the latch member 3' is held in the state where the through holes 3f, 3g' are fitted onto the restraint projections 2h', 2i', the lower surface of the joggle portion 3c' of the latch member 3' is in contact with the upper surface of the ejector 6', and the joggle portion 3c' can not engage the latch hole 12a' of the tongue 12'.
In this state, as the tongue 12' is inserted into the buckle 1' in a direction .delta.' in order to connect the tongue 12' to the buckle 1', the ejector 6' is pressed by the end of the tongue 12' to move rearwardly and is displaced from the lower surface of the joggle portion 3c' of the latch member 3'. Therefore, the latch member 3' pivots in the counter-clockwise direction .alpha.' about the shafts 3a', 3b' by the force of the latch spring 7' and the joggle portion 3c' latches to the latch hole 12a' of the tongue 12'. Thus, the tongue 12' engages and connects to the buckle 1' as shown in FIG. 22.
During this process, the rotational displacement of the latch member 3' is accompanied by the rotation of the control wings 4a', 4b' of the lock member 4' in the counter-clockwise direction .alpha.', so the wings 4a', 4b' are spaced apart from the side edges of the restraint projections 2h', 2i'and move relative to the latch member 3' in the direction .beta.', i.e. in the longitudinal direction of the latch member 3'. The control wings 4a', 4b'close the through holes 3f', 3g' of the latch member 3' so that the lower ends of the restraint projections 2h', 2i' come in contact with the control wings 4a', 4b' and are thus prevented from entering into the through holes 3f', 3g'. As a result, even when abnormal impact is applied to the buckle 1', e.g. in case of a vehicle collision, since the upper surfaces of the control wings 4a', 4b' are in contact with the lower ends of the restraint projections 2h', 2i', the latch member 3' is limited not to pivot in the clockwise direction so that the latch member 3' is held in the engagement position. Consequently, the tongue 12' and the buckle 1' are prevented from canceling the engagement therebetween.
For releasing the tongue 12' from the buckle 1', the operational portion 5a' of the operational button 5' is pressed in a direction .zeta. with a finger. Then, the lock member press portion 5c' of the operational button 5' comes in contact with the pressed portion 4d' of the lock member 4' and presses the pressed portion 4d'. Accordingly, the lock member 4' moves relative to the latch member 3' in the direction .eta.' so that the wings 4a', 4b' are displaced from the through holes 3f', 3g' of the latch member 3' to open the through holes 3f', 3g', thereby allowing the restraint projections 2h', 2i' to enter into the through holes 3f', 3g'.
As the operational button 5' is pressed in the direction .zeta.' further, the spring supporting and press portion 5b' comes in contact with the spring supporting and pressed portion 3h' and presses the spring supporting and pressed portion 3h' against the force of the latch spring 7'. The latch member 3' then pivots in the clockwise direction .epsilon.' so that the joggle portion 3c' is displaced upwardly to escape from the latch hole 12a' of the tongue 12' and the tongue 12' is pressed by the ejector 6' to move in the direction .gamma.' and is thus released from the buckle 1'.
At this point, the ejector 6' is positioned beneath the joggle portion 3c', so the release of the operational button 5' causes the operational button 5' to become in the inoperative position by the force of the latch spring 7' and the force of the button spring 9'. In addition, the latch member 3' pivots slightly in the counter-clockwise direction .alpha.' so that the lower surface of the joggle portion 3c' comes in contact with the upper surface of the ejector 6', thereby holding the latch member 3' in the upper or non-engaged position.
In this way, the tongue 12' can be easily engaged with and released from the buckle 1'.
In this conventional buckle 1', however, the lock member 4' not only follows the pivotal movement of the shafts 3a', 3b' of the latch member 3' to pivot in the same directions (the directions .alpha.', .epsilon.') thereof but also moves linearly in the longitudinal directions of the latch member 3' (the directions .beta.', .eta.'). That is, the movement of the lock member 4' is complex. Even though the movement of the lock member 4' is complex, of course, the buckle must conduct the control of the latch member 3' by the lock member 4'. It is more desirable to simplify the movement of the lock member 4' as simple as possible. The simplification of the movement of the lock member 4' is preferable to improve the controllability of the latch member 3'.